1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device and, in particular, the present invention relates to an improved method for forming a titanium nitride film using chemical vapor deposition.
2. Description of the Related Art
The chemical vapor deposition of titanium nitride will be described as an example of a conventional method for manufacturing a semiconductor device for forming a titanium nitride film in a contact hole using the CVD. FIGS. 1A through 1D are cross-sectional views showing the conventional method in the order of steps.
As shown in FIG. 1A, a lower electrode having a thickness of 500 nm is formed on an interlayer insulating film on a silicon substrate 1. An element separation oxide film 2 is formed and a predetermined amount impurities are introduced into the silicon substrate 1 thereby forming a diffused layer 3. An insulating film 4 having a thickness of 1500 nm is then deposited and a connection hole 5 is formed on the diffused layer 3.
Next, as shown in FIG. 1B, a titanium film 6 having a thickness of 10 nm and a titanium silicide film 7 having a thickness of 20 nm are deposited on the insulating film 4 and on the diffused layer 3, respectively, by the chemical vapor deposition, while using titanium tetrachloride, hydrogen and argon as material gas.
As shown in FIG. 1C, the titanium film 6 on the insulating film 4 is nitrided with ammonia thereby forming a titanium nitride film 8.
As shown in FIG. 1D, a titanium nitride film 9 having a thickness of 20 nm is formed on the titanium nitride film 8 and the titanium silicide film 7 is formed by chemical vapor deposition, using titanium tetrachloride, ammonia and nitrogen as material gases.
The problem with the conventional method for manufacturing a semiconductor device mentioned above is as follows.
The growth of a titanium nitride film by chemical vapor deposition using titanium tetrachloride requires a temperature of about 600.degree. C. to reduce residual chlorine. Due to this, stress of about 1 GPa is generated. If such a large degree of film stress is generated, films are cracked or peeled off thereby causing the erosion of WF.sub.6 by W-CVD in later steps and the silicon substrate is deformed thereby causing junction leakage. As a result, a contact electrode cannot have stable electric characteristics.
Meanwhile, Japanese Patent Application Laid-Open No. 61-156837, for example, discloses a method for relaxing stress by injecting Ar ions into a titanium nitride film of 150 nm in thickness. This manufacturing method is intended to reduce the influence on an upper aluminum wiring. If the titanium nitride film formed by sputtering is present at the bottom of a contact hole on a silicon substrate, use of Ar ions disadvantageously causes much damage to the silicon substrate.